Navigational instrument



2 SHEETSSHEET 1 Filed Feb. 26, 1948 Inventor Altar/1e ys Feb. 3, 1953 J. w. BARNES 2,627,180

NAVIGATIONAL INSTRUMENT Filed Feb. 26, 1948 2 SHEETS-SHEET 2 dillllll I}! l l.

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Attorneys Patented Feb. 3, 1953 NAVIGATIONAL INSTRUMENT Jeifery Walton Barnes, Farnborough, England, assignor, by mesne assignments, to Kelvin & Hughes Limited, Glasgow, Scotland, a British company Application February 26, 1948, Serial No. 11,141 In Great Britain June 19, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires June 19, 1965 4 Claims.

This invention relates to navigational or position-indicating instruments and refers more particularly to instruments intended for use in aircraft for giving an indication of the position of the aircraft relatively to the earths surface.

It is known to provide aircraft with apparatus for indicating air position in which an element driven proportionally to the distance travelled is combined with an element driven according to the direction of travel, so as to resolve the distance travelled into cardinal components and thus determine the distance travelled in any direction, such as north-south and east-west. One form of such apparatus, known as an air position indicator is described in British patent specification No. 558,619. Such apparatus incorporates a mechanism which is driven proportionally to the distance travelled in a north-south direction and another mechanism which is driven proportionally to distance travelled in an east-west direction.

The object of this invention is to provide an instrument which can be used in conjunction with such an air position indicator for indicating the position of the aircraft relative to the earths surface by plotting the position on a map or chart.

According to this invention the instrument comprises, elements adapted to be driven proportionally to cardinal components of air distance from a starting or datum point, a device for resolving wind speed and direction into cardinal components mechanism for adding the cardinal components of wind speed and direction to the corresponding components of air distance to produce combined cardinal component value proportional to the movement of the aircraft relative to the earths surface and two members, one of which is adapted to carry a map or chart and the other carrying a pointer, one of which members is adapted to be moved to by said mechanism proportionally to the combined cardinal component values of movement relatively to the earths surface.

In a preferred form the instrument comprises elements driven proportionally to cardinal components of the distance travelled relative to the air, a vector resolving mechanism adapted to be set in accordance with Wind speed and direction and to resolve the wind speed and direction into cardinal components, co-ordinating mechanism driven by said elements and said vector resolving mechanism for combining the cardinal components of air distance with the respective cardinal components of wind speed and direction to give cardinal components of distance relative to the earths surface, a cylindrical member and a support for a map or chart, said member having a pointer adapted to be moved by said co-ordinating mechanism in accordance with the cardinal components of distance relatively to the earths surface to give indication of position on the map or chart.

The pointer may also be movable to maintain it in line with the aircraft heading and thus indicate on the map or chart the direction in which the aircraft is travelling.

Preferably, the pointer consists of a beam of light formed by an optical projector having a light source, a graticule and a lens adapted to project by a light beam, at graticule image on the map or chart and means driven by said coordinating mechanisms for deflecting the light beam proportionally to the cardinal components of distance relative to the earths surface, so that the graticule image indicates position on the map or chart.

The invention will be more clearly understood by reference to the drawings accompanying the provisional specification in which:

Fig. 1 is schematic diagram of the instrument.

Fig. 2 is a sectional elevation of the projector system.

Fig. 3 is a sectional plan of the differential gearing.

In order that the two elements which are to be driven proportionally to the distance travelled relative to the air can be conveniently actuated from the mechanisms in the air position indicator previously referred to, two electrical stepby-step transmitters of well-known form are located in the air position indicator and are driven by two shafts of said mechanisms whose rotational speeds are proportional respectively to the north-south and east-west components of the distance travelled. Although it is convenient to use such transmitters, it will be appreciated that this method of transmitting the drive from the air position indicator to the elements of an instrument according to this invention are not essential, as the required motions could be transmitted by other means as, for instance, flexible driving cables.

In the illustrated embodiment however, electrical transmitters of the type mentioned are used and these are connected by electrical wires to repeater motors l, 2. One of these repeater motors marked 1 is driven proportionally to the distance travelled in a north-south direction and the other marked 2 is driven proportionally to the distance travelled in an east-west direction.

These repeater motor drive mechanisms which are substantially identical in form and the mechanism driven by the repeater motor I will be specifically described, like parts in the mechanism driven by the repeater motor 2 being indicated by like references.

The motor I drives through a differential gear 3, the output shaft 4 carrying a pinion 5 forming part of a gear train 6 comprising a large gear wheel 7 and a small gear Wheel 8 meshing with the pinion 5. Either of these gear wheels 7 or 8 can be shifted into driving engagement with the gear Wheel 9 which is connected through a clutch Hi to a shaft formed with a lead screw I2 driving a nut I3. On an extension of the shaft H a setting knob I4 is provided to enable the mechanism to be manually set to a starting or datum point.

As previously stated the mechanism driven by the motor 2 is similar to that driven by the motor I but the shaft instead of carrying the lead screw has a driving connection through gear wheels I 5 and It with a shaft 7 arranged at right angles to the shaft II, the shaft carrying a lead screw l8 for driving a nut IS.

The wind speed and direction setting and vector resolving mechanism comprises a drum 2%? bearing two scales, one of which is a wind speed scale 2| and the other a wind direction scale 22, both engraved on the same drum. The drum is driven by a gear wheel 23 fixed thereon meshing with a pinion 24 which is rotated by means of a knob 25 to set wind direction in the scale 22 against a fixed pointer 23. The wind speed setting knob 2? drives through a pinion 28, a gear wheel 29 fixed to a spindle 36 extending axially through the drum and having a ring 3| mounted so as to rotate with the gear wheel 29, said ring carrying datum lines 32, five of which are provided equally spaced around the ring 3|, so that one of these datum lines is always visible for any setting of wind direction. The knob at 27 is rotated until one of the datum lines 32 is opposite to the wind speed on the scale 2|. Thus the drum 28 carrying the said two scales is set according to wind direction and with the wind speed scale 2| positioned according to wind direction, the ring 3|, in being rotated to bring its datum line 32 against the wind speed value on scale 2| will be moved proportionally both to the wind direction and to wind speed. A stud 33 on the frame of the ring 3| and eccentrically located to the axis of the ring is connected by a link 34 to a second stud 35 fixed to a plate 36. The plate 36 is slidably mounted on guide rods 31 extending from blocks 38 fixed to the drum 2B. The link 34 thus slides the plate 36 along the rods 31 when the ring 3| is rotated. The plate 35, which is rotated with the drum 2|] and also displaced by the link 34, carries a wind operating pin 39 which is caused by said movement of the plate 36 to describe an arc of a circle and to be moved into a position which is determined both by the setting of the drum 2% in accordance with wind direction and the setting of the ring 3| in accordance with Wind speed. Consequently, the position of the wind operating pin 39 will be determined by both wind speed and direction and will represent the wind vector. To resolve the north-south and east-west components of the wind from the position of the wind operating pin 39 representing the wind vector, a known form of vector resolving mechanism comprising two slotted bars 48, 4| are provided arranged mutually at right angles to each other and engaging the wind operating pin 39. The mechanism is assembled so that when a wind direction from north-south is set, the guide rods 3? for the sliding plate 35 are parallel to the east-west slotted bar 4i, and thus as wind speed is set the wind operating pin 33 moves in this slot without causing any movement of the slotted bar 4|. Each slotted bar 49 or 4| is fixed to a slide rod 42 which is mounted to slide in an axial direction. Thus the movement of one of the rods is proportional to the east-west component and the movement of the other rod is proportional to the north-south component of the wind speed.

The slide rods 42 control the position of friction wheels 43 contacting the upper and lower discs 45, 46, the wheels 43 and the discs 45, 46 constitute an infinitely variable gear. Each wheel 43 is mounted on a shaft 4? to which is fixed a long pinion 48 carried by the shaft 43. The wheels 43 are spring loaded on to the surface of the discs 45, 46 by the tension spring 5|] extending between the shaft 43.

The discs 45, 46 are locked together and driven at a constant speed by means of a worm 5! and a worm wheel 52, the worm being driven from a constant speed motor 53.

The effective lengths of the slide rods 42 are adjusted so that for zero wind setting the contact points of the wheels 43 coincide with the centre of the discs 45, 46. When wind speed and direction are set, slide rods 42 position the wheels 43 on the surface of the discs 45, 46 until the displacement of the wheels from the disc centres is proportional to the two cardinal components of the wind. Since the discs 45, 48 are driven at constant speed, the rotation of the wheels 43 is respectively proportional to the north-south and and east-west components of the wind and hence he number of rotations of the wheels 43 and the long pinions 48 will be proportional to the northsouth and east-west components of the wind. The rotation of the wheels 53 are transmitted by way of the long pinions 48 to the contrate wheels 54, 55 and thence through the shafts 55, 51 to the differential gears 3.

The two differential gears indicated generally at 3 which combine the cardinal components of air distance with the cardinal components of wind are of the planet type. The mortars or 2 rotate a gear wheel 65 which in turn rotates a gear wheel 6| there two gear wheels rotating freely on the output shaft 4. A worm 62 on the shaft 56 or 5? rotates a worm wheel 63 which in turn rotates a gear wheel E54, and the worm wheel 63 and E4 also rotate freely on the output shaft 4. Two planetary wheels 55, 55, one of which meshes only with the gear wheel 6| and the other which meshes only with the gear wheel 64 are mounted in a cage 3'1 which is fixed to the output shaft 4, thus the cage is rotated and with it the output shaft 4 at half the algebraic sum of the movements imparted by the worm 62 and the motor or 2. The differential gears thus compound the component of air mileage from the motors with the component of wind mileage from the vector resolving mechanism and rotate the shaft 4 proportional to ground mileage.

The gear train 5, 6, i and 8 is mounted on a fiat plate 67* which is pivoted about the shaft 4, so that it can be rocked about the axis of the shaft 4 into either of two positions, in one of which the gear wheel 1 meshes with the gear wheel 9 and. the other in which the gear wheel 8 meshes with the gear wheel 9. The plate 81* is rocked by means of the double links 68 pivoted at 69 to a gear selector lever I0. This change speed gearing enables the device to be used with either small or large scale maps of the type which will be hereinafter referred to.

From the foregoing, it will be understood that the lead screws I2 and I8 will be driven by the mechanisms previously described by amounts proportional to distance travelled relative to the ground in an east-west direction and in a northsouth direction respectively, and these rotary movements will move the nuts I3 and I9 by corresponding amounts.

. The optical projector shown more clearly in Fig. 2 comprises a reflecting mirror II and a lens I2, both of which are mounted in the cylindrical mirror tube I3. The mirror II is pivoted at I I in bearings carried in the mirror tube I3 and is operated by an arm IOI terminating in a flat surface I02 extending parallel to the pivot axis II* but offset from the said pivot axis by an amount equal to the radius of the ball I03 with which the surface I02 is held in contact by the spring I04. The ball I03 is carried on an arm I05 made fast to the shaft 13* which shaft rotates in bearings fixed to the frame of the instrument (not shown).

The bracket 91 which is free to turn on the shaft 13* carries an arm I4 normally contacting a peg 98 on the nut I9, and carries a second arm I to which the spring I00 is attached and a third arm I01 for an adjustable screw I00 which normally touches the arm I05. The spring I00 is anchored to the frame of the instrument at The spring I04 applies a torque to the mirror II which ensures that normally the surface I02 on the arm IOI touches the ball I03 and that the arm I touches the screw I08, but this torque is insufficient to lift the arm I4 from the peg 98 against the pull of the spring I 00.

Since the distance between the centre of the ball I03 and the axis of the shaft 13* is equal to that between the axis of the shaft 13* and the axis II*, when the tube I3 is in its central position and the axis II* is parallel to the shaft 13*, the mirror will move through half the angle moved through by the arm I05. Also, since the reflected rays from the mirror II turn through twice the angle turned through by the mirror II about the axis II* it follows that the reflected rays move through the same angle as the arm I05. If with the mirror in any other position than the 45 angle the tube I3 be rotated about its axis with the mirror locked to the tube I3, the reflected rays would trace a hyperbola on the chart 88, and as a straight line trace is required the ball I03 and flat surface I02 connection between the arms IM and I05 was specially designed to give small rotation of the mirror about its axis II* when the tube I3 is rotated to give a linear trace of the rays on th chart. In the particular position illustrated in which the mirror is at 45 to the optical axis and in which the reflected rays from the mirror II are at right angles to the rays from the lens I2 no such small rotation of the mirror is required and is not given by the arrangement described and illustrated because in this particular position the ball is located on the optical axis of the light source. The mirror tube I3 is mounted so that it can rotate about its axis for north-south traverse which is communicated to the tube by an arm I5 connected to the nut I3.

A tube I6 carrying a graticule I1 is mounted coaxially with the mirror tube and is rotatable by a worm wheel I8 driven by a worm I9 and gearing 80, 8I from a compass repeater motor 82 of known type which rotates the graticule tube, so that the graticule will indicate when projected by the mirror the aircraft heading relatively to the map or chart. Preferably, the graticule I1 is not mounted directly on the graticule tube but is mounted on an adjustable sleeve 83 which is clamped to the graticule tube. Rotation of the sleeve 83 enables the graticule image to be synchronised with a course scale 84 used in conjunction with a fixed pointer on the mirror tube to indicate the course being taken. Axial adjustment of the sleeve 83 enables the graticule image to be focussed.

The graticule II is directly illuminated by means of a lamp 8B and projects an image of the graticule through the lens I2 on to the mirror II for which it is reflected on to the map or chart 88 carried by a table beneath the mirror tube 13.

To obtain syncronisation with the compass controlling the repeater motor 82, the gear wheel is formed with a slotted spindle 81, so that the gear wheel 80, worm I9, worm wheel I8 and the graticule tube can be rotated until the course scale indication is correct. The worm I9 is carried on a splined shaft and small angles of rotation of the graticule may be effected, in addition to those produced by the repeater motor 82 by sliding the worm along the splined shaft. The position of the worm I9 on the worm shaft is controlled by a compensating lever system, including the arm 90, the shaft 9|, the arm 92 and the link 93 connected to the mirror tube I3 so that the north-south rotation of mirror tube is added to the normal compass rotation of the graticule. Without this compensating mechanism the graticule image would rotate as it traverses the map in a north-south direction and the arrow head would then no longer indicate the aircraft heading. The whole instrument is intended to be fixed in the aircraft at a definite height above the navigators table indicated at '88 which will carry the map on which the ground position is to be indicated by the graticule image projected as hereinbefore described. A suitable type of map is that known as a conical orthomorphic projection. The map must be aligned with respect to the axis of the projector and to facilitate this the graticule image projected from the mirror II can be rapidly traversed in alignment with the projector axes by the operation of a traversing lever 96 fixed on the pivot 13*. The bracket 91 carrying the arm I4 is so arranged that by operating the lever 96 the arm I4 can be moved laterally against the spring I00 out of contact with the pin 98 to allow the mirror II to be swung counter-clockwise in the direction of the axis of the tube 13 while the mirror II can be swung clockwise by rotating the lever 98 against the action of the spring I04, in which case the arm I05 moves away from the screw I08.

I claim:

1. In a navigational instrument having output members driven proportional to the combined air distance and wind speed in north-south and east-west directions respectively, a stationary map, an optical projection mechanism above said map having a rotatable cylindrical mirror tube, a reflector pivotally mounted in said tube and rotatable therewith, a lens mounted in said tube, an adjustable graticule tube mounted coaxially with respect to said mirror tube, .a source of light for projecting the graticule image on said reflector so as to project said image on said map, means operable with a repeater compass to ro tate said graticule so as to indicate on the map the aircraft heading, mean-s driven by one output member for rotating the cylindrical mirror tube proportional to the compensated distance traversed in a north-south direction. and means driven by the other output member for pivoting said reflector within said tube proportional to the compensated distance traversed in an east-West direction.

2. In a navigational instrument having output members driven proportional to the cornbined air distance and wind speed in north-south and east-West directions respectively, a stationary map, an optical projection mechanism above said map having a rotatable cylindrical mirror tube, a reflector pivotally mounted in said tube and rotatable therewith, a lens mounted in said tube, an adjustable graticule tube mounted caxially with respect to said mirror tube, a source of light for projecting the graticule image on said reflector so as to project said image on said map, means operable with a repeater compass to rotate said graticule so as to indicate on the map the aircraft heading, means driven by one output member for rotating the cylindrical mirror tube proportional to the compensated distance traversed in a north-south direction, mean driven by the other output member for pivoting said reflector within said tube proportional to the compensated distance traversed in an east-west direction, and means for imparting a small addition-a1 rotation to said reflector about its pivotal axis when said mirror tube is rotated so as to give a linear trace to the rays projected .on the map.

3. In a navigational instrument a lens system, a reflector, means for projecting a light beam along the axis of said lens system and on to said reflector, means for rotating the reflector about the axis of the l ns system according to one variable, means for rotating the reflector about an axis perpendicular to the axis of the lens system according to another variable, a direction in dicating graticule interposed in said light beam, and means for orient-ating the graticule about the axis of said lens system so that the graticule image will indicate the direction as Well as the position.

4. In a navigational instrument a, lens system, a reflector, means for projecting a light beam along the axis of said lens system and on to said reflector, means for rotating the reflector about the axis of the lens system according to one variable, means for rotating the reflector about an axis perpendicular to the axis of the lens system according to another variable, means for imparting a small additional rotation to said reflector about said perpendicular axis when the reflector is rotated about the lens system axis so as to give a linear trace to the rays projected by said reflector, a direction indicating graticule interposed in said light beam, and means for orientating the graticule about the axis of said lens system so that the graticule image will indicate the direction as well as the position.

JEFFERY WALTON BARNES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,412,997 Bonneau et a1. Apr. 18, 1922 1,985,266 Smith et a1. Dec. 25, 1934 2,115,558 Becker Apr. 26, 1938 2,143,011 Joha'sz Jan. 10, 1939 2,314,497 Ha-rgrave et al Mar. 23, 1943 2,395,351 Sohn Feb. 19, 1946 2,444,708 Masner et a1. July 6, 1948 2,495,296 Springer Jan. 24, 1950 

